1. Field of the Invention
The present invention relates to a linear guide apparatus including a guide rail, a slider travelling freely on the guide rail, a ball circulating paths for balls which are interposed between the guide rail and the slider, and in particular, to a linear guide apparatus designed to prevent the leakage of lubricating oil supplied to the ball circulating paths.
2. Description of the Relevant Art
A prior art linear guide apparatus of this type is disclosed, for example, in U.S. Pat. No. 4,472,003.
The linear guide apparatus includes an elongated guide rail having ball rolling grooves formed in both side surfaces extending in the axial direction, a slider main body mounted to straddle the guide rail and movable in relation thereto, and having ball rolling grooves formed respectively opposing the ball rolling grooves of the guide rail and having axial through holes, serving as ball passages, formed in parallel with the ball rolling grooves, end caps fixed respectively to opposite ends of the slider main body, and a multiplicity of balls rollably inserted in the ball rolling grooves. Each of the end caps has ball circulating paths of a half-doughnut shape respectively extending between a corresponding ball rolling groove and a through hole of the slider body, and has a feed oil channel for feeding oil to the ball circulating paths.
When the slider moves on the guide rail in the axial direction, the balls pass through the through holes and the ball circulating paths and rollably circulate through the ball rolling grooves, allowing the slider to move smoothly in the axial direction. In this case, lubricant is supplied to the balls in the ball circulating paths through the feed oil channel provided in the end cap. As a result, smooth rolling of the balls can be insured.
However, the feed oil channel in the end cap of the prior art linear guide apparatus is a mere recessed channel formed in a plane portion of the end surface of the end cap in contact with the end surface of the slider main body. Consequently, even when small screws are used to fix the end cap to the slider main body, it is difficult to bring both the end surfaces of the slider and the end cap into close and complete contact with each other due to errors in the geometry such as surface finishes and flatness of both the end surfaces. As a result, a minute gap is caused between the end surfaces. In this case, if grease is used as the lubricant, there will be no problem, but if liquid lubricating oil is used, it tends to leak to the outside of the feed oil channel.
In particular, when the oil is supplied from the lower end cap with the guide rail in a perpendicular condition, the oil will leak from the contact surface, of the end cap with the guide rail, and sufficient oil will not be supplied to the balls. As a result, the problem is involved in that the life of the linear guide apparatus is shortened.